Gas turbine compressor



Dec. 29, 1964 c. H. PAUL. ETAL. 3,163,003

GAS TURBINE COMPRESSOR Original Filed Oct. 25, 1954 3 Sheets-Sheet 1 IN VE N TORS CARLTON H. PAUL HOMER J. WOOD ATTORNEY Dec. 29, 1964 c. H. PAUL ETAL. 3,153,003

GAS TURBINE COMPRESSOR Original Filed Oct. 25. 1954 s Sheets-Sheet 2 Fig.2

/N VE' N TORS CARL TON H. PAUL HOMER J. WOOD A TTORNEY Dec. 29, 1964 c. H. PAUL ETAL 3,163,003

GAS TURBINE COMPRESSOR Original Filed Oct. 25, 1954 3 Sheets-Sheet 3 Fig.4

wvm'rons CARLTON H. PAUL HOMER J. WOOD @ZLQMMW ATTORNEY United States Patent Office 3,163,003 GAS TINE COMPRESSOR Carlton H. Paul, Scottsdale, Ariz., and Homer 1. Wood,

Sherman Oaks, Calif., assignors to The Garrett Corporation, Los Angeles, Calif, a corporation of California Original application Oct. 25, 1954, Ser. No. 464,276, new Patent No. 3,914,694, dated Dec. 26, 1961. Divided and this application Feb. 27, 1961, Ser. No. 91,951 7 Claims. (Cl. 60-4936) This invention relates to and finds utility in gas turbines. It has particular application to gas turbine compressors.

This application is a true division of the application of Carlton H. Paul and Homer J. Wood, Serial No. 464,276, filed October 25, 1954, now Patent No. 3,014,694, dated December 26, 1961, for a Gas Turbine and Sea-ling Means Therefor.

The term gas turbine compressor, as used herein, defines a hot-gas operated turbine which drives a compressor arranged to furnish air to a combustor which delivers hot gas to the turbine, and which supplies bleed air for pneumatic power purposes, this last constituting all or a major part of the useful output of the machine.

Small gas turbines for use in aircraft should have a structural arrangement which is rugged, compact and efficient. Thermal insulation of such gas turbine combustion chambers, while highly desirable, has posed some problems, particularly in aircraft installations wherein size and weight are important considerations.

In small, compact gas turbine compressors, it has also been desirable to attain a construction wherein a centrifugal compressor is provided with an efficient peripheral diffuser arranged in closely coupled relationship with the combustion chamber of the associated gas turbine.

Centripetal turbine wheels require means for sealing gases at one side thereof whereby leakage of the motive fluid is maintained at a minimum. Such seals have previously caused a substantial axial pressure differential across the turbine wheel whereby high speed bearings supporting the same were unduly loaded by axial thrust.

In accordance with the present invention a gas turbine compressor may be powerful, compact, efficient, and may have a relatively cool external surface surrounding the combustion chamber thereof. In order to provide a compact, powerful and efficient gas turbine compressor, the centrifugal compressor is provided with an efficient peripheral diffuser arranged in closely coupled relationship with the combustion chamber of the gas turbine. Such a construction includes an outer casing which surrounds the combustion chamber and turbine inlet torus and the diffuser disposed at the outlet of the compressor, permitting close coupling of the compressor and turbine, and also providing an efficient, thermally regenerative insulation of the external portions of the machine from combustion chamber heat radiation.

In addition, the present invention embraces means for sealing the turbine against motive fluid leakage and provides for a minimum fluid pressure differential on the turbine wheel axially thereof. Such an arrangement pro vides for minimum axial loading of the high speed bearings which support the turbine shaft. The present combination of a centrifugal gas turbine wheel and sealing means for motive fluid includes an arrangement wherein fluid pressure in the seal opposes pressure of the motive fluid around the turbine wheel, thereby preventing the motive fluid from leaking through the seal around the turbine shaft. This arrangement permits the seal structure to be close to the shaft and permits a partial balance of the pressures on opposite sides of the wheel to minimize the pressure differential thereacross.

It is an object of the present invention to provide a small gas turbine compressor which is powerful, efficient and compact.

Another object of the invention is to provide a gas turbine compressor which is particularly suitable for installation in aircraft.

Another object of the invention is to provide a gas turbine compressor having a novel arrangement for insulating external portions thereof from combustion heat radiation therefrom.

A further object of the invention is to provide a gas turbine construction wherein a centrifugal compressor is provided with an eificient peripheral difluser arranged in a novel closely coupled relationship with the combustion chamber 'of the gas turbine.

A still further object of the invention is to provide novel means for sealing gases at one side of a gas turbine wheel whereby leakage of motive fluid therefrom is maintained at a minimum.

An additional object of the invention is to provide a gas turbine wheel having a seal around its shaft permitting a minimum pressure differential across the Wheel whereby axial loading of the high speed bearings supporting the wheel is maintained at a minimum.

Further objects and advantages of the invention will be apparent from the following specification, appended claims, and accompanying drawings, in which:

FIG. 1 is a longitudinal axial sectional view of a gas turbine compressor according to the present invention;

FIG. 2 is an enlarged fragmentary sectional view taken on the same plane as that shown in FIG. 1 and illustrating in detail features of the turbine structure thereof;

FIG. 3 is a fragmentary sectional view taken from the line 33 of FIG. 2; and

. FIG. 4 is a vertical transverse sectional view taken through the combustor and gas inlet chamber of the gas turbine compressor shown in FIG. 1 on the plane indicated by the line 44 of such figure.

The gas turbine compressor as shown in FIG. 1 of the drawings is provided with a two-stage compressor which is mounted on a shaft 10. The first stage of the compressor includes a double-sided impeller 11 which delivers compressed air to ducts 12 communicating with the inlet of an impeller 13 which forms the second stage of the compressor. The impeller 13 is a centrifugal impeller, the periphery of which is surrounded by a diffuser 14 having an annular passage 15 extending from a radial direction to an axial direction. Positioned in the diffuser are vanes 14a disposed normally to the compressor axis. Spaced from the vanes 14a and at right angles thereto are vanes 14b which are disposed at the outlet of the. diffuser 14. The vanes 14a are primarily diffuser elements, while the vanes 1% are combined diffuser and flow straightening elements. The diffuser vanes are surrounded by a casing structure composed of casing sections 16 and 17. Straightening of flow in the plenum casing 17 provides for more efficient entry of air into a combustor 21. The casing section 16 is arranged in conforming relation to the curvature of the passage 15 and forms an annular structure which completely surrounds the impeller 13. The generally cylindrical casing section 17 is fixed to the casing section 16 by means of flange bolts 18. The casing 17 forms a duct or plenum adapted to receive compressed air which issues from the diffuser as indicated by the arrows in FIG. 1.

The casing section 17 surrounds the outlet portion of the vanes 14b and also surrounds a combustion and gas entry chamber 19 which communicates with the peripheral inlet of a centripetal turbine wheel 20. The entry chamber 19 is of annular shape and surrounds the centripetal wheel 20 and communicates with the combustor 21 which receives compressed air from the interior of the casing 17.

Patented Dec. 29, 1964- Air which is delivered by the compressor impeller 13 flows through the casing 17 and combusto-r 21 to the interior of the entry chamber 19, then through conventional nozzles 29A to the periphery of the turbine wheel 20. It will be noted from FIGS. 1 and 4 that the combustor 21 is completely enclosed by the casing section 17 and discharges tangentially into the gas entry chamber 19. As mentioned above, the chamber 19 is of annular configuration and is disposed in planes normal to the axis of rotation of the turbine Wheel. The combustor, as shown in FIG. 4, includes a perforated cylindrical wall portion connected with the gas entry chamber member 19 and a fuel spray nozzle carried by the end wall structure of the combustor. This end wall structure closes the end of the combustor and also an opening in the casing section 17 through which parts of the combustor may be withdrawn for servicing when a separable retaining band of the well-known Marman type is removed. The turbine Wheel 20 is provided with a shaft portion 22 which is supported on bearings 23 and 24. The shaft portion 22 is coupled to the compressor shaft 10 by means of a spline member 25. Surrounding the turbine shaft 22 is a two-part labyrinth type seal generally indicated at 26.

The structure'of seal 26 is shown in detail in FIG. 2. Carried by the shaft 22 is a labyrinth seal member 2?. The seal member 27 is an annular structure having a bore 28 fitted on the shaft 10 in fluid tight relationship therewith. The seal member is provided with an exterior portion having labyrinth grooves 29 which run in close proximity to a bore portion 30 of a stationary bushing 31 which forms the second part of the seal assembly and is fixed to a frame element 32 of the gas turbine compressor, the interior of which frame element 32, through tube 32a, is in communication with atmospheric pressure. The seal member 27 is also provided with a broad external groove 33 which communicates with a duct 34' arranged to have fluid pressure applied thereto from the interior of the casing 17; thus, compressor output air may flow through the duct 34 and into the external groove 33 of the labyrinth seal member 2'7. It will be seen that labyrinth grooves 2? are disposed on opposite sides of the groove 33 whereby fluid pressure therein is applied across the labyrinth grooves 29 and may thereby oppose combustion gas pressure around the turbine wheel 20. In the arrangement shown in FIG. 1, compressor output pressure in the casing 17 exceeds the pressure of combustion gas around the turbine wheel Ztl, and therefore fluid pressure in the groove 33 of the seal member 27 will effectively oppose combustion gas pressure tending to permit gas to leak through or pass the seal 27 axially of the shaft 22 into the relatively low pressure interior of frame element 32. It will be uuderstoodthat flow of air from the compressor through the casing 1'7 must pass the combustor 21 before reaching the turbine wheel 20. Thus, the inevitable flow restriction in the combustor causes the combustion gas to be at a lower pressure than that of the compressor output air communicating with the duct 34 and the groove 33 in the labyrinth seal member 27;.

Coupled in fluid tight relationship with the bushing 31 and the frame element 32 is a diaphragm 35. This diaphragm 35 extends radially from the seal structure to a i frame element 36 near the periphery of the turbine wheel 20-; The frame element 36 is clamped by suitable fasteners 36A to the periphery of the diaphragm 35 adjacent a nozzle box structure 37 which communicates with the entry chamber 19. Also fixed to the frame element 36 by means of bolts 38 is a back shroud member 39 which is arranged in close proximity to the blades and back portions of the turbine wheel 20. The diaphragm 35 prevents leakage of fluid at the peripheral portion 40 of the shroud 39 and also prevents leakage through its central opening 41 and around the bushing 31 disposed therein.

It will be understood that the labyrinth seal member 2'7 cooperating with sealing diaphragm "5 provides a seal structure which prevents leakage of combustion gas from the area of the turbine wheel 20 into the interior of the casing 17 and around the shaft 22. This seal structure provides a novel cooperative combination with the turbine wheel 29. The turbine wheel 26 is a generally starshaped wheel having a central hub structure provided with radially disposed cantilever blade portions, as illustrated particularly in FIG. 3. Since the actual diameter of the seal member 27 is relatively small in proportion to the overall diameter of the turbine wheel 2%, it does not expose a large area at the back of the wheel to a pressure substantially different from that at the front side of the wheel through which combustion gas flows. With reference to FIG. 2, it will be seen that both front and back portions of the wheel hub structure are subject to the combustion gas pressure, and therefore the axial pressure differential on the wheel is at a minimum, thus maintaining axial loading of bearings 23 and 24 at a minimum.

An oil cooler 4-3 is disposed in the air inlet to the compressor impeller ll. Air flowing through the oil cooler 43 cools oil which is used for lubricating and cooling various bearings and moving elements of the gas turbine compressor.

Operation of the gas turbine compressor as shown in FIG. 1 is substantially as follows:

When the shafts l0 and 22 are rotating in coupled relation to each other, as hereinbefore described, the first stage 11 of the compressor delivers relatively low pressure air to the inlet of the second compressor stage 13, whereupon the pressure of the air is increased and delivered through the diffuser 14 to the interior of the casing 1'7. Since the diffuser 14 extends around the entire periphery of the centrifugal compressor 13, extending from a radial direction to an axial direction, and exhausting directly into the casing 17, a very efficient arrangement is obtained, particularly where it is desirable to arrange a centrifugal compressor in a compactly coupled relationship with the combustion chambers of a gas turbine. As compressed air is delivered from the diffuser into the casing 17, it flows straight after passing the vanes 14b and then passes around and into the entry chamber 19 which is operating at an elevated temperature. Regenerative heat exchange with the straightened air entering the combustor 21 is accomplished, and at the same time, the exterior of the casing l7 is maintained at a relatively low temperature. The heated air entering the combustor 21 provides for thermal efiiciency in the operation of the gas turbine, thereby rendering it more economical to operate. As combustion gas passes from the chamber 19 through the turbine wheel 23, it exhausts outwardly through a conduit 42.

Air pressure in the casing 17 is applied through duct 34 to the groove 33 in the seal member 2'7. hereinbefore described, compressor output pressure exceeds combustion gas pressure around the wheel 2%; therefore, air pressure existing in the groove 33 opposes leakage of combustion gas through the labyrinth portions 23 of the seal member 27, thereby preventing leakage of combustion gas along the shaft 22 of the turbine wheel 20. At the same time, combustion gas is prevented from leaking away from the area of the wheel 29 by the sealed diaphragm 35, as hereinbefore described. The diaphragm 35 permits the shround member 39 to be installed wit liberal tolerances at its periphery 4t and central opening 41, whereby thermal expansion does not cause displacement or warpage of the adjacent structures. Thus, the diaphragm 35 permits reasonable tolerances to be employed in the assembly of the frame elements with the shroud 39, and at the same time prevents leakage therethrough. The diaphragm 35 forms a continuation of the seal structure surrounding the laybrinth seal member 27 which in turn is fitted in fluid tight relationship with the shaft 22. As hereinbefore described, a pressure balance of the combustion gas on the hub of the the As wheel permits the wheel 20 to be operated in such a manner that minimum axial loading of the bearings 23 and 24 may be attained. In the operation and servicing of a gas turbine compressor, as shown in FIG. 1, the external skin surface of the casing 17 is cool relative to the surface of the entry chamber 1f, which provides an important safety feature, particularly when the gas tubbine compressor is installed in close quarters aboard an aircraft, for example.

The invention has been shown and exemplified by its use in a gas turbine compressor. It will be apparent at once to those skilled in the art that it is applicable to gas turbines in which the useful output may be principally or entirely jet thrust or shaft power, or any combination thereof.

We claim:

1. A gas turbine comprising: a centrifugal compressor wheel; a centripetal turbine wheel coupled with said compressor Wheel to impart rotary motion thereto; diffuser means having a pair of Walls spaced to provide an annular passage extending radially from the periphery of said compressor wheel and terminating in an axially extending outlet; an annular gas entry chamber disposed in a plane normal to the axis of rotation of said compressor and turbine wheels and having an annular radially inwardly directed gas nozzle means registering with the periphery of said turbine Wheel to direct gases thereto; a combustor having a perforated outlet tube connected and communicating substantially tangentially with said gas entry chamber; and a casing surrounding the outlet of said diffuser, said gas entry chamber, and said combustor, said casing serving as a means for conducting compressed fluid from the diffuser outlet to the combustor inlet.

2. A gas turbine comprising: a centrifugal compressor wheel; a centripetal turbine wheel coupled with said compressor wheel to impart rotary motion thereto; diffuser means having a pair of walls spaced to provide an annular passage extending radially from the periphery of said compressor wheel and terminating in an axially extending outlet; an annular gas entry chamber disposed in a plane normal to the axis of rotation of said compressor and turbine wheels and having an annular radially inwardly directed gas nozzle means registering with the periphery of said turbine wheel to direct gases thereto; a combustor having a perforated outlet tube connected and communicating substantially tangentially with said gas entry chamber; and a casing surrounding the outlet of said diffuser, said gas entry chamber, and said combustor, said casing serving as a means for conducting compressed fluid from the diffuser outlet to the combustor inlet and having an axially extending centrally disposed tubular portion aligned with said turbine wheel and constituting the exhaust outlet therefor.

3. A gas turbine comprising: a centrifugal compressor rotor means having a double-entry, single-outlet first stage and a single-entry, single-outlet second stage; conduit means connecting the outlet of the first stage with the single entry of the second stage; a centripetal turbine wheel coupled with said compressor rotor means to impart rotary motion thereto; diffuser means having a pair of Walls spaced to provide an annular passage extending radially from the periphery of the second stage of said compressor rotor means and terminating in an axially extending outlet; an annular gas entry chamber disposed in a plane normal to the axis of rotation of said compressor rotor and turbine wheel and having an annular radially inwardly directed gas nozzle means registering with the periphery of said turbine wheel to direct gases thereto; a combustor having a perforated outlet tube connected and communicating substantially tangentially with said gas entry chamber; and a casing surrounding the outlet of said diffuser, said gas entry chamber, and said combustor, said casing serving as a means for conducting compressed fluid from the diffuser outlet to the combustor inlet and having an axially extending centrally disposed 6 tubular portion aligned with said turbine wheel and constituting the exhaust outlet therefor.

4. A gas turbine comprising: a centrifugal compressor wheel; a centripetal turbine wheel coupled with said compressor wheel to impart rotary motion thereto; diffuser means having a pair of walls spaced to provide an annular passage extending radially from the periphery of said compressor wheel and terminating in an axially extending outlet; an annular gas entry chamber disposed substantially concentric with and in a plane normal to the axis of rotation of said turbine wheel, said gas entry chamber having an annular radially inwardly directed gas nozzle means registering with the periphery of said turbine wheel to direct gases thereto; a combustor disposed with the longitudinal axis thereof in a plane extending substantially normal to the axis of rotation of said turbine wheel, said combustor having a perforated outlet tube connected and communicating substantially tangentially with said gas entry chamber; and a casing surrounding the outlet of said diffuser, said gas entry chamber, and said combustor, said casing serving simultaneously to conduct compressed air from the diffuser outlet to the combustor inlet and confine said compressed air around said gas entry chamber to absorb heat therefrom.

5. A gas turbine comprising: a centrifugal compressor wheel; a centripetal turbine wheel coupled with said compressor wheel to impart rotary motion thereto; diffuser means having a pair of walls spaced to provide an annular passage extending radially from the periphery of said compressor wheel and terminating in an axially extending outlet; an annular gas entry chamber disposed substantially concentric with and in a plane normal to the axis of rotation of said turbine Wheel, said gas entry chamber having an annular radially inwardly directed gas nozzle means registering with the periphery of said turbine wheel to' direct gases thereto; a combustor disposed with the longitudinal axis thereof in a plane extending substantially normal to the axis of rotation of said turbine wheel, said combustor having a perforated outlet tube connected and communicating substantially tangentially with said gas entry chamber; a casing surrounding the outlet of said diffuser, said gas entry chamber, and said combustor, said casing simultaneously serving to conduct compressed air from the diffuser outlet to the combustor inlet and confine said compressed air around said gas entry chamber to absorb heat therefrom; and a fuel supply nozzle and combustor end cap detachably connected with said casing at the end of said combustor.

6. A gas turbine, comprising: a frame; shaft means journalled in bearings mounted in said frame; a centrifugal compressor rotor secured to one end of said shaft means; a centripetal turbine wheel provided on the opposite end of said shaft means; compressor output diffuser means surrounding the periphery of said compressor wheel, said diffuser means being arranged to turn compressor output flow from a radial direction at its inlet to an axial direction at its outlet; an annular gas entry chamber disposed in a plane normal to the axis of rotation of said compressor rotor and turbine wheel and having an annular radially inwardly directed gas nozzle means registering with the periphery of said turbine wheel to direct gases thereto; a combustor having an outlet directed substantially tangentially into said gas entry chamber; and a casing communicating with the outlet of said diffuser means and surrounding the bearing supporting portion of said frame, said gas entry chamber and said combustor, the construction of said frame providing for the use of compressor outlet air to cool the bearings supported thereby in addition to the cooling of the gas entry chamber walls and supplying combustion supporting air to said combustor.

7. A gas turbine, comprising: a frame; shaft means journalled in bearings mounted in said frame; a centrifugal comprepsor rotor secured to one end of said shaft means; a centripetal turbine wheel provided on the oppo- 7 site end of said shaft means; compressor output diffuser means surrounding the periphery of said compressor wheel, said difiuser means being arranged to turn compressor outlet flow from a radial direction at its inlet to an axial direction at its outlet; an annular gas entry chamber disposed in a plane normal to the axis of rotation of said compressor, rotor and turbine wheel and having an annular radially inwardly directed gas nozzle means registering with the periphery of said turbine wheel to direct gases thereto; a coinbustor having a perforated outlet tube connected and communicating substantially tangentially With said gas entry chamber; and a casing communicating with the outlet of said diffuser means and surrounding the bearing supporting portion of said frame, said gas entry chamber, and said combustor, said casing receiving compressor output air and applying the same E5 to said bearings, the exterior of said gas entry chamber, and to said cornbustor through the perforations in said outlet tube.

References Cited in the file of this patent I UNITED STATES PATENTS Hodgson Sept. 15, 1953 2,695,499 VJalker Nov. 30, 1954 2,706,150 Lloyd Apr. 12, 1955 2,855,754 Giannotti Oct. 14, 1958 FOREIGN PATENTS 491,080 Canada Mar. 10, 1953 666,416 Great Britain Feb. 13, 1952 699,865 Great Britain Nov. 18, 1953 

1. A GAS TURBINE COMPRISING: A CENTRIFUGAL COMPRESSOR WHEEL; A CENTRIPETAL TURBINE WHEEL COUPLED WITH SAID COMPRESSOR WHEEL TO IMPART ROTARY MOTION THERETO; DIFFUSER MEANS HAVING A PAIR OF WALLS SPACED TO PROVIDE AN ANNULAR PASSAGE EXTENDING RADIALLY FROM THEPERIPHERY OF SAID COMPRESSOR WHEEL AND TERMINATING IN AN AXIALLY EXTENDING OUTLET; AN ANNULAR GAS ENTRY CHAMBER DISPOSED IN A PLANE NORMAL TO THE AXIS OF ROTATION OF SAID COMPRESSOR AND TURBINE WHEELS AND HAVING AN ANNULAR RADIALLY INWARDLY DIRECTED GAS NOZZLE MEANS REGISTERING WITH THE PERIPHERY OF SAID TURBINE WHEEL TO DIRECT GASES THERETO; A COMBUSTOR HAVING A PERFORATED OUTLET TUBE CONNECTED AND COMMUNICATING SUBSTANTIALLY TANGENTIALLY WITH SAID GAS ENTRY CHAMBER; AND A CASING SURROUNDING THE OUTLET OF SAID DIFFUSER, SAID GAS ENTRY CHAMBER, AND SAID COMBUSTOR, SAID CASING SERVING AS A MEANS FOR CONDUCTING COMPRESSED FLUID FROM THE DIFFUSER OUTLET TO THE COMBUSTOR INLET. 